Someone asked me recently what quality I'd most want in a co-founder. I said something like "good judgment" or "strong communication skills" — reasonable answers. But thinking about it more, I keep coming back to something harder to measure: grit.

Angela Duckworth's research on grit — the combination of passion and perseverance for long-term goals — has stuck with me since I read it. The findings that surprised her most surprised me too: talent alone doesn't predict achievement. In fact, talented people who lack perseverance often underperform less talented people who keep going.

The startup test for grit

Starting a company is a long-term experiment in grit. Almost everything takes longer than you expect. Almost everything is harder than you anticipated. Almost everything that was going well eventually runs into serious trouble.

The question isn't whether you'll encounter setbacks — you will, continuously. The question is what you do when you do.

I've noticed a pattern in the founders I respect most. When things go wrong, they have a quality I can only describe as stubbornness about the underlying problem. Not about their specific solution — they're often willing to throw that away. But about the problem itself, about the users they're trying to serve, about the fundamental value they believe they can create.

They don't quit the problem. They quit bad answers to the problem.

Passion matters more than I thought

Duckworth's framework pairs passion with perseverance. I used to think passion was the softer, less important half. Perseverance sounds more like work. But I've changed my mind.

Passion is what makes sustained perseverance possible. You can white-knuckle your way through a setback. You cannot white-knuckle your way through years. The people who maintain energy and commitment across the long haul of building a company aren't just disciplined — they genuinely care about what they're doing at a level that goes beyond professional motivation.

For me, the problem of making meals and grocery shopping easier for busy families isn't abstract. It's something I experience every week. When the product isn't working well, it bothers me personally, not just professionally. That bothers me in a way that motivates rather than discourages.

I think this is what "working on something you care about" really means, at the operational level. Not just that you find the domain interesting. But that the problem is personal enough that solving it means something to you that doesn't go away when the going gets hard.

Grit at the company level

There's an organizational version of this too. Companies have collective grit — a shared resilience that determines whether they bend or break when things get hard.

I think it comes from the same place as individual grit: genuine belief in what you're building and clarity about why it matters. Teams that have that tend to stay together and push through things that would break apart teams that are more loosely committed.

This is one reason I'm thoughtful about who we hire at 10X. Skills matter. But I also want to know: does this person actually care about the problem we're solving? Are they the kind of person who gets more energized or more defeated when things don't work?

Not to be confused with stubbornness

One caveat: grit can look like stubbornness, and stubbornness is destructive. The difference, I think, is in what you're persevering toward.

Grit means staying committed to the goal while staying open about the path. If your users are telling you something is wrong, grit doesn't mean ignoring them. It means using that feedback to find a better path while staying committed to reaching the destination.

Stubbornness means staying committed to the path when evidence says it's the wrong one. That's not perseverance. That's denial.

The founders I admire have learned to tell the difference in themselves. That's a skill too — knowing when to persist and when to pivot, and having the honesty to make that call clearly.